209.长度最小的子数组(滑动窗口+双指针) 难度：中等 语言：C++

class Solution {
public:
    int minSubArrayLen(int target, vector& nums) {
        int left = 0, right = 0;
        int sum = 0;
        int len = 0;
        int min_len = INT_MAX;
        while(right < nums.size()){
            while(right < nums.size() && left <= right){
                if(sum >= target){
                    min_len = min(min_len, len);
                    break;
                }
                sum += nums[right];
                len++;
                right++;
            }

            while(sum >= target){ //当总和减去left的数后仍然大于target，则继续将left的值减去。
                sum -= nums[left];
                len--;
                left++;
                min_len = min(min_len, len+1);
            }
        }
        if(min_len == INT_MAX)
            return 0;
        else
            return min_len;
    }
};